The present invention relates to a pattern forming method and a method of manufacturing a device having a fine pattern. The device having a fine pattern represents, for example, a semiconductor device or a recording medium that has a fine pattern and requires a microscopical processing technology for the manufacture thereof.
A lithography technology using photoresist, etc. is widely used nowadays in the technical field requiring a microscopical processing technology as in the manufacture of a semiconductor device. The lithography technology permits forming a relatively fine pattern.
However, the degree of integration of a semiconductor dievice such as DRAM is made higher and the density of a recording medium such as DVD is made higher in recent years. As a result, attentions are paid to the development of a microscopical processing technology of nanometers scale.
In the lithography technology, the resolution can be increased by forming, for example, a resist film very thin. To be more specific, where a resist film formed on a film to be etched is irradiated with light, the photoresist is sensitive to both the incident light emitted from a light source and a reflected light from the film to be etched. The reflected light from the underlying layer runs through an optical path differing from that of the incident light or is scattered within the resist film so as to give an adverse effect to the resolution. The adverse effect is rendered prominent with increase in the thickness of the resist film. Therefore, a high resolution can be achieved by forming the resist film very thin.
For improving the resolution by this method, it is considered most effective to use a monomolecular film, e.g., a Langmuir-Blodget film (hereinafter referred to as LB film), as a resist film. In fact, various researches are being made on the use of an ultra thin film such as a monomolecular film as a resist film.
For example, M. J. Lercel et al. report in "J. Vac. Sci. Technol. B11(6), 2823 (1993)" that a monomolecular film of n-octadecyl trichlorosilane formed on a surface of a SiO.sub.2 substrate or a monomolecular film of n-octadecane thiol formed on a surface of a GaAs substrate was exposed to an electron beam to form a pattern of the monomolecular film. M. J. Lercel et al. also report that a grating having a width of 25 nm was formed by applying a wet etching to the substrate surface using the pattern thus obtained as a mask.
Also, the technology of exposing a monomolecular film to an ion beam is disclosed by P.C. Reike et al. in "Langmuir 10, 619 (1994)" and by G. Gillen et al. in "Appl. Phys. Lett. 65, 534 (1994)". K. K. Berggren et al. disclose the technology of exposing a monomolecular film to an atomic beam in "Science 269, (1995)". Further, the technology of exposing a monomolecular film to light using a probe of a scanning probe microscope is disclosed by L. Stockman et al. in "Appl. Phys. Lett. 62, 2935 (1993)", by S. Yamamoto et al. in "Jpn. J. Appl. Phys. 34, 3396 (1995)", by C. R. K. Marrian et al. in "Appl. Phys. Lett. 64, 390 (1994)" and by Y. -T. Kim et al. in "Langmuir 8, 1096 (1992)". It is also reported in each of these documents that a pattern of scores of nanometers scale was formed successfully.
However, it is reported by M. J. Lercel et al. in "J. Vac. Sci. Technol. B11 (6), 2823 (1993)" that an ultra thin film such as a monomolecular film has fine defects and, thus, fails to exhibit a sufficient resistance to etching for using the monomolecular film as an etching mask. Therefore, it was difficult to form a fine pattern with a high resolution by the methods exemplified above.